Mechanism of action of TOP2-directed anticancer drugs

TOP2靶向抗癌药物的作用机制

• 批准号: 6782758
• 负责人: LEROY F LIU
• 金额: $ 28.69万
• 依托单位: UNIV OF MED/DENT NJ-R W JOHNSON MED SCH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-03-10 至 2008-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6782758
• 关键词: DNA damage; DNA topoisomerases; antineoplastics; biological signal transduction; carcinogenesis; cell death; genetically modified animals; laboratory mouse; neoplasm /cancer pharmacology; peptidases; pharmacokinetics; ubiquitin

DESCRIPTION (provided by applicant): The long-term goal of this application is to determine the mechanism of action of topoisomerase II (TOP2)-directed anticancer drugs. In addition to their antitumor activities, TOP2-directed anticancer drugs;uch as VP-16 have been associated with the development of therapy-related acute myelogenous leukaemia (AML). Indeed, our preliminary studies have shown that VP-16 behaves as a stage I tumor promoter in the mouse skin carcinogenesis model. TOP2-directed anticancer drugs are known to trap both TOP2 isozymes, TOP2 alpha and TOP2 beta, into their respective covalent complexes with DNA known as cleavable or cleavage complexes. These two TOP2 isozymes are regulated differently during the cell cycle and most likely perform different functions. However, the differential roles of these two TOP2 isozymes in the antitumor and carcinogenic activities of TOP-directed anticancer drugs remain unclear. Our recent studies have demonstrated that TOP2 beta but not TOP2 alpha cleavage complexes induced by the TOP2-directed anti-cancer drug, VP-16, trigger ubiquitin/26S proteasome-dependent degradation of TOP2 beta (TOP2beta down-regulation). This is the first demonstration of a TOP2 isozyme-specific cellular response to TOP2-directed anticancer drugs. TOP2beta down-regulation is dependent on RNA transcription but not new protein synthesis. Concurrent with TOP2 beta down-regulation, the large subunit of RNA polymerase II, but not other proteins, is also degraded by 26S proteasome. These and other results have suggested that a ubiquitin/26S proteasome pathway(s) is activated locally in the vicinity of the arrested RNA polymerase elongation complexes, leading to the degradation of the TOP2 beta-DNA covalent complex. We further hypothesize that degradation of the TOP2 beta-DNA covalent complex results in exposure of theTOP2-concealed double-strand breaks, which could contribute to both tumor cell death and DNA sequence rearrangements/carcinogenesis. Elucidation of the differential cellular responses to TOP2 cleavage complexes formed by TOP2 isozymes may form the foundation for future development of TOP2 isozyme-specific anticancer drugs. The objective of the current application is to characterize the ubiquitin/26S proteasome pathway induced by TOP2-directed anticancer drugs and to explore the biological consequences of TOP2 beta down-regulation in tumor cell death and carcinogenesis.

描述（申请人提供）：本申请的长期目标是确定拓扑异构酶II（TOP2）定向抗癌药物的作用机制。除了抗肿瘤活性外，TOP2 导向的抗癌药物（例如 VP-16）还与治疗相关的急性髓性白血病 (AML) 的发展有关。事实上，我们的初步研究表明，VP-16 在小鼠皮肤癌发生模型中充当 I 期肿瘤促进剂。已知 TOP2 定向抗癌药物可将 TOP2 同工酶 TOP2 α 和 TOP2 β 捕获到其各自与 DNA 的共价复合物中，称为可裂解或裂解复合物。这两种 TOP2 同工酶在细胞周期中受到不同的调节，并且很可能执行不同的功能。然而，这两种 TOP2 同工酶在 TOP 导向抗癌药物的抗肿瘤和致癌活性中的不同作用仍不清楚。我们最近的研究表明，由 TOP2 定向抗癌药物 VP-16 诱导的 TOP2 β 裂解复合物，而非 TOP2 α 裂解复合物，会触发泛素/26S 蛋白酶体依赖性 TOP2 β 降解（TOP2β 下调）。这是针对 TOP2 抗癌药物的 TOP2 同工酶特异性细胞反应的首次演示。 TOP2beta 下调取决于 RNA 转录，而不是新蛋白质合成。在 TOP2 beta 下调的同时，RNA 聚合酶 II 的大亚基（而非其他蛋白质）也被 26S 蛋白酶体降解。这些和其他结果表明，泛素/26S 蛋白酶体途径在停滞的 RNA 聚合酶延伸复合物附近被局部激活，导致 TOP2 beta-DNA 共价复合物降解。我们进一步假设 TOP2 beta-DNA 共价复合物的降解导致 TOP2 隐藏的双链断裂暴露，这可能导致肿瘤细胞死亡和 DNA 序列重排/癌变。阐明细胞对 TOP2 同工酶形成的 TOP2 裂解复合物的差异反应可能为未来开发 TOP2 同工酶特异性抗癌药物奠定基础。本申请的目的是表征 TOP2 定向抗癌药物诱导的泛素/26S 蛋白酶体途径，并探讨 TOP2 β 下调在肿瘤细胞死亡和癌变中的生物学后果。